What are electricity meters composed of?
Analysis of the functional modules of electricity meters
1. Power Supply Module
As the "energy center" of the electricity meter, its core function is to convert the high-voltage AC 220V into low-voltage DC 12V, DC 5V, and DC 3.3V to power other modules. There are three common types:
Transformer: First converts 220V AC to approximately 12V AC, then rectifies and stabilizes it to obtain the target voltage. It has low power and high stability, but is susceptible to electromagnetic interference.
Capacitive voltage reduction: Uses the capacitive reactance of a capacitor to limit the working current. It is small in size and low in cost, but its disadvantages are low power and high self-consumption.
Switching power supply: Modulates the voltage through periodic switching of electronic switching devices. It has low power consumption, small size, and a wide voltage regulation range, but it has high-frequency interference and is more expensive.
The selection should be based on product functions, meter casing size, cost, and regional policy requirements.
2. Display Module
The core function is to display electricity consumption data. Common types include digital tubes, counters, ordinary LCDs, dot-matrix LCDs, and touch LCDs. Among them, digital tubes and counters can only display a single type of electricity consumption data, which can no longer meet the needs of smart grids for displaying multiple types of electricity data. LCDs are currently the mainstream, and the type can be selected based on the complexity of the display content.
3. Storage Module
Used to store meter parameters, electricity consumption, historical data, etc. Common devices are EEPROM chips, ferroelectric chips, and Flash chips, each with different application scenarios:
Flash chip: A type of flash memory, used to store temporary data, load curves, software upgrade packages, etc.
EEPROM chip: Electrically erasable and programmable, can be written 1 million times, suitable for data that needs frequent updates, such as electricity consumption. It is low in price and can meet the storage needs of the electricity meter throughout its entire lifespan. Ferroelectric Chip: Offers up to 1 billion write cycles, retains data even without power, and boasts advantages in high density, high speed, and low power consumption, making it suitable for high-frequency storage scenarios. However, it is relatively expensive.
4. Sampling Module
Responsible for converting high-current, high-voltage signals into smaller signals for subsequent data acquisition. Current sampling commonly uses shunts, current transformers, and Rogowski coils, while voltage sampling primarily employs high-precision resistive voltage dividers.
5. Metering Module
The core function is to acquire current and voltage analog signals and convert them into digital signals. It is divided into single-phase and three-phase metering modules.
6. Communication Module
This is the core of data transmission and interaction, supporting the refined management of smart grids and human-machine interaction in the Internet of Things. Early systems primarily used infrared and RS485 communication, but now various options such as PLC、LoRaWAN、4G、GPRS、NB-IoT are available. The selection should be based on the application scenario and the advantages and disadvantages of each communication method.
7. Control Module
Using a built-in magnetic latching relay, it manages the power supply to the load based on power data, control schemes, and real-time commands. Core functions include: disconnecting the relay to protect the circuit during overcurrent/overload conditions, time-based power on/off control, power disconnection due to insufficient prepaid credit, and receiving commands for remote control.
8. MCU Processing Module
As the "brain" of the electricity meter, it is responsible for various data calculations, instruction conversion and execution, and coordinating the collaborative work of each module to ensure overall functionality.
Electricity meters are complex electronic metering products that integrate technologies from multiple fields, including power supply, power measurement, communication, display, and storage. Deep integration of these modules and technologies is necessary to create a stable, reliable, and accurate device.
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